This invention relates to a leading-out device for a lead wire of a DC motor wherein a lead wire portion connected to a main circuit conductor of the motor and led outside thereof, is improved.
FIG. 3 is a side view of a starter motor wherein a lead wire is led from a direct current motor portion to the outside thereof. A reference numeral 1 designates a starter motor composed as follows. A numeral 2 designates a DC motor, wherein a rear bracket 4 is connected to a rear end of a yoke 3 and a front bracket 6 is connected to a front end thereof through an intermediate bracket 5. Inside thereof, a speed reducing gear device is connected to an armature and a pinion 15 is extended therefrom through an overrunning clutch. A numeral 16 designates an electromagnetic switch wherein a lead wire 12 extended from the motor 2 to the outside thereof, is connected to a main circuit terminal (M terminal) 17. A numeral 13 designates a grommet fitted to a cut-off portion of the yoke 3 through which the lead wire 12 passes and 14, an insulation tube fitted to the lead wire 12.
A circuit diagram of the DC motor 2 is shown by FIG. 4. A numeral 7 designates an armature, 8, brushes and 9, field coils connected to a conductor 10 to which the lead wire 12 is connected at a connecting portion 11.
When current flows in an electromagnetic switch 16, the contact of the circuit is closed, and a current from a storage battery flows from the main circuit terminal 17 to the lead wire 12 and to the main circuit of the DC motor 2 thereby rotating the armature 7. In the meantime, a plunger of the electromagnetic switch 16 is operated, a shift lever (not shown) is swiveled and a pinion 15 is moved forward through an overrunning clutch to mesh with a ring gear of an internal combustion engine. The rotation of the armature 7 is reduced by the speed reducing gear device and rotates the pinion 15 through the overrunning clutch. In this way, the ring gear is rotated and the engine is started.
FIG. 5A is a sectional diagram of a conventional leading-out device for a lead wire. An end of the lead wire 12 composed of twisted wires is connected to the connecting portion 11 of the connecting conductor 10 of the motor 2 by a brazing material. As shown in FIG. 5B by a sectional diagram, a lead wire 12 passing through the grommet 13 made of a gummy material is a twisted-wire conductor composed of a great number of copper wires. Especially, in the starter motor, since a large current flows in the lead wire 12 and in view of the vibration resistance, the diameter thereof is magnified.
In the conventional leading-out device for a lead wire, the outer configuration of the lead wire 12 is circular and thick. The lead wire 12 reaches inside of the yoke 3 through the grommet 13. To maintain a clearance between the lead wire 12 and the inner field coil 9, the motor 2 is elongated in the axial direction, which hampers the downsizing thereof.
Furthermore, in the above conventional leading-out device for a lead wire, in passing the leading-out portion of the lead wire 12 through the grommet 13, a hole of the grommet 13 has an interference to provide a waterproof performance. Therefore the operation is difficult. Furthermore, a variation of the protruding length of the leading-out portion which passes through the grommet 13 should be avoided and the protruding length should conform to a predetermined length. Therefore, the operation becomes more difficult.